This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present disclosure that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Auto-stereoscopic display devices (either based on the use of a parallax barrier, or based on the use of a micro-lens array) enable the display of multi-view content. As mentioned in the document US 2014/0168390, when a user is positioned at an “optimal distance”, He perceives only a first view from one eye, and a second view from another eye (see FIG. 5 of document US 2014/0168390, and the optimal viewing distance “OVD”). Therefore, He perceives a 3D effect, without having to wear 3D glasses (either passive or active glasses). The set of positions at an optimal viewing distance defines regions in space named sweet spots or also viewing spots, i.e. these regions located in front of auto-stereoscopic display device are regions where a user can only perceive one view per eye, enabling the viewing of a 3D content without interferences (see for example the article entitled “Comparative study of auto stereoscopic displays for mobile devices” by A. Boev and A. Gotchev). It should be noted that, the higher a number of views auto-stereoscopic display devices provide, the smaller the sweet spots are.
Usually, an auto-stereoscopic display device comprises:                a display panel which is an array of pixels (such display panel can be for example a TFT LCD screen (for Thin-film-transistor liquid-crystal display screen)) that can be viewed as an image forming means, and        an optical filter positioned in front of such display panel that controls the diffusion directions of rays of light emitted by the display panel. The optical filter can be either a parallax barrier (or a combination of parallax barriers, that intend to block light in some directions), or a lenticular sheet (that intends to refract the received light from pixels), or an integral lens sheet (as in document EP 0780727).        
More precisely, a pixel comprises several sub-pixels as explained for example in document US 2014/0226205. As detailed in FIG. 3 of document US 2014/0226205, a pixel can be made of three sub-pixels, and each of these sub-pixels is associated with a primary color (blue, red or green) and with an image view. An example of an arrangement of these sub-pixels in a display panel is depicted in the FIG. 4 of document US 2014/0226205, in the case that three images views are delivered by the auto-stereoscopic display device (the information of such arrangement is given in a correspondence map which associated each sub-pixel of said auto-stereoscopic display device with a view). At last, when all the sub-pixels associated to one view (as in the FIG. 5 of document US 2014/0226205, with a view 1) are perceived by an eye of a viewer, an image associated with the view 1 is visualized by the viewer.
In the case that the auto-stereoscopic display device can handle n different image views, with n an integer greater or equal to two, it is possible to generate such n different images views from only two views (named stereoscopic images) as explained in the document US 2013/0050187. Usually the process of generating such n different images views can be done in a device delivering content for each view (such device is named a renderer or a device delivering content for each view). Usually such renderer is comprised in the auto-stereoscopic display device itself.
Hence, in the case that there are several auto-stereoscopic display devices to address, which supports different number of views, each auto-stereoscopic display device has a renderer for generating/providing the expected number of views associated with the concerning auto-stereoscopic display device. In order to reduce the cost of the auto-stereoscopic display devices, it could be better to suppress some electronic components in such devices as for example the renderer.
The proposed technique is directed to renderers that are not comprised in auto-stereoscopic devices.
Moreover, it is proposed a technique that is more flexible than the one in the state of the art. Indeed, for the moment, in the case that an auto-stereoscopic display device handles n different images views, with n an integer greater or equal to two, the renderer delivers n different images views. There is no flexibility in that kind of approach in the sense that the renderer only delivers a fixed number of images views. Hence, there is a need to provide a technique that provides more flexibility.